WPF: How to know the selection is come from datagrid or from ListBox?

Question

Our application has a page which includes DataGrid and ListBox.
Both ItemSource are binding to PlateCells.
public ObservableCollection<CellVM> PlateCells
public class CellVM : BaseViewModel
public CellVM(int wellNumber)
WellNumber = wellNumber;
Row = wellNumber / define.NumberofWellsInRow;
Col = wellNumber % define.NumberofWellsInRow;
// row and col are 0-based
public int WellNumber { get; set; }
public int Row { get; set; }
public int Col { get; set; }
bool _isSelected;
public bool IsSelected
get { return _isSelected; }
set
_isSelected = value;
OnPropertyChanged("IsSelected");
string _sampleId;
public string SampleId
{ get { return _sampleId; }
set
_sampleId = value;
OnPropertyChanged("SampleId");
when a cell is selected, the cell will be highlight in both DataGrid and ListBox.
We also implement SelectAll button for both DataGrid and ListBox.
And SelectAll is ToggleButton. First time click is select All cells and second time click, it will unselect All cells.
What we notice when SelectAll button is click, all cells in both DataGrid and List box  are highlight.
After that click on a grid any cell, all cells becomes unselected in both DataGrid and ListBox.
 We assume this the behavior from DataGrid, after click SelectAll and click any cell in DataGrid will remove all selection and only highlight one cell in the datagrid.
However, this is behavior does not happen in ListBox. click any cell in ListBox only unselect that cell and not unselect all cells.
So we need to know click(selection) is coming from DataGrid or ListBox and take different actions.
How do we know the click is coming from DataGrid or ListBox? Thx!
JaneC

Answer 1

>>How do we know the click is coming from DataGrid or ListBox? Thx!
It depends on where in the code you want to be able to determine this. In the view model class you cannot really know if the user clicked in the ListBox or in the DataGrid because the view model knows nothing (and shouldn't know either) about any of these
controls. It only exposes a property that may be set from anywhere.
Handling the GotFocus event for any or each of the controls seems to be a good solution because then you can take the appropriate action depending on which control was focused/clicked.
You could of course move the code that is being executed when the GotFocus event occurs, i.e. the code in your event handler, from the code-behind of the view to the view model class by using a command in the view model class and then hook up the GotFocus
event to this command using event triggers:
<DataGrid>
<i:Interaction.Triggers>
<i:EventTrigger EventName="GotFocus" >
<i:InvokeCommandAction Command="{Binding YourCommand}" />
</i:EventTrigger>
</i:Interaction.Triggers>
</DataGrid>
How to do this is a topic of its own though. Please refer to my blog post about how to handle events in MVVM for more information:
http://blog.magnusmontin.net/2013/06/30/handling-events-in-an-mvvm-wpf-application/. You will need to reference an assembly that is part of the Expression Blend SDK which you can download from here:
http://www.microsoft.com/en-us/download/details.aspx?id=10801.
Anyway, as mentioned, handling the GotFocus event seems like a good idea here since you cannot determine which control that was clicked in the setter of the source property in the view model class.
Hope that helps.
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